Navigational guide system



March 26, 1940. J. H. HAMMOND, JR

NAVIGATIONAL GUIDE SYSTEM 3 Sheets-Sheet 1 Filed Jan. 23 1937 Eur-Fromm INVENTOR JOHN HAYS HAMMOND, JR. BY

motzoi QM March 26, 1940.

J. H. HAMMC DND, JR 2,194,548 NAVIGATIONAL GUIDE SYSTEM Filed Jan. 23, 1957 :5 Sheets-Sheet 2 INVENTOR JOHN HAYS HAMMOND, JR.

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NAVIGATIONAL GUIDE SYSTEEH Filed Jan. 23, 1937, :5 Sheets-Sheet s we 5 aw INVENTOR 39 ,gs 13 JOHN HAYS HAMMONILJR.

BY i3 Patented Mar. 26, 1940.

UNITED STATES PATENT" OFFICE 6Claims- This invention relates to navigational systems and more particularly to a system for determining the direction and distance of a craft from a given point.

An object of the invention is to provide a' novel and relatively simple system of the above type which is suitable for use on small boats or other locations where expensive and complicated equipment and skilled attendants are unavailable.

Another object is to provide a novel system which may be used to indicate the position of the vessel with respect to a given contour line rep resenting the approach to dangerous waters.

Another object is to provide a system of the above type which can be easily calibrated to insure the correct operation thereof.

Various other objects and advantages will be apparent as the nature of the invention is more fully disclosed.

go A feature of the invention consists in the provision of a rotating radio beam located, for example, on an island or other point which is surrounded by dangerous waters.

In accordance with one embodiment of the o5 invention, the strength oi the beam is varied automatically as it rotates, in such a manner that a predetermined, constant field strength occurs at all points along the contour line about the dangerous locality. This variation in beam strength is obtained by varying the power of the transmitter in synchronism with and at a predetermined function of the rotation of the beam.

A designating signal may also be transmitted,

such as predetermined groups of dots and dashes or voice signals which are varied in accordance with the angular position of the beam to indicate the direction of the beam at the time the signals are heard. For example; a certain group of dots and dashes may indicate North or the signal may be modulated with the word North.

This would be timed in synchronism with the rotating beam to occur when the beam points in that direction. Other suitable signals would indicate the time when the beam is pointing at other points of the compass.

In one embodiment this designating signal is used to modulate the rotating beam so that the beam characteristics can beused to determine both distance and direction. ever, can be separately transmitted if desired.

The approaching vessel can determine its direction and distance by receiving the rotating beam and observing, as the beam sweeps past the vessel in its rotation, the maximum field strength and the direction designating signal at the time of greatest signal intensity. The former indicates the distance from the predetermined contour line and the latter indicates the direction with respect to the transmitter. When the 30 field strength at its maidmum point exceeds a The signals, howpredetermined value, the navigator is warned that he is at the contour line and is approaching dangerous waters.

In a further embodiment of the invention, the rotating beam is maintained at a constant inv tensity, although the direction designations are impressed thereon in the manner above mentioned. In determining the location of the receiver, the field strength is measured and the measurement is referred to a chart which shows 0 the known field strengths at different distances from the transmitter and which may have the contour line superimposed thereon so that the exact location of a vessel with respect to the danger line can be easily determined. 5

Another feature of the invention consists in the provision of calibrating means at the receiver so that the correct operation thereof can be assured. In one embodiment, this calibrating means comprises a local oscillator and a local gq source of modulation having suitable indicating means and adjustments so that they may be ad- Justed to a fixed standard. This standard energy is then applied to the input of the receiver to permit the receiver to be calibrated accordingly. 25 With, the receiver calibrated in this manner an accurate measurement of the rotating beam can be assured.

Various other features of the invention consist in the details of construction and combina- 3( tions of parts hereinafter more fully set forth.

Although the invention can be embodied in various forms and is capable of various uses. the broader aspects thereof will be better understood by referring to the following description, taken 31 in connection with the accompanying drawings, in which one embodiment thereof has been set forth for purposes of illustration only.

In the drawings?" Fig. 1 is a diagrammatic view of one embodi- 4 ment of the transmitting apparatus used in this invention;

Fig. 2 is a diagrammatic view showing the positions of a vessel approaching dangerous waters;

Fig. 3 is a fragmentary view of a modified Q form of the invention used to replace part of the mechanism shown in Fig. l; and

Fig. 4 is a schematic diagram of the receiver and calibrating apparatus to be used in connection with the transmitter shown in Fig. 1. 6

Like reference characters denote like parts in the several figures of the drawings.

In the following description and in the claims parts will be identified by specific names for con- 7 venience, but they are intended to be as generic 5 in their application to similar parts as the art will permit.

Referring to the accompanying drawings and more particularly to Fig. 1, the embodiment of the invention shown comprises an antenna or n beam radiator II and a reflector assembly l2 consisting of a plurality of reflecting radiators I3 arranged in the form of a parabola with its axis along the radio beam line H and with the radiator II at the focus. The reflecting radiators |3 are mounted in a frame l5 which is rotatably mounted with respect to the radiator ll. Secured to the frame I5 is a beveled gear l6, which meshes with a beveled pinion I 1 secured to a shaft l8.

Secured to the shaft I8 is a second beveled.

pinion l9, which meshes with a beveled gear secured to a rotatable shaft 2|. Seared to the shaft 2| is a cam 22 the shape of which'is described in connection with Fig. 2.

A beveled gear 25 is secured to the shaft I8 and meshes with a beveled pinion 26 which is driven at a constant speed by a motor 21.

Secured to the shaft |8 is a third beveled pinion 30 which meshes with a beveled gear 3| secured to a rotatable shaft 32. Secured to the shaft 32 isa signal record disc 33 which is provided with dots 35 and dashes 36. These dots and dashes are arranged in groups such as 31, 38, 39 etc. each of which comprises a dash 36 and one or more dots 35. The number of dots increases from group to group. That is, group 31 has one dot, group 38 two dots, group 33 three dots, etc. A key 40 is operated by the dots and dashes 35 and 38 and is connected to control the tone oscillator of an amplifier modulator 43. A microphone 34 is also connected to the amplifier modulator 43 to impress voice signals thereon when desired. I

The beam radiator II is supplied .with energy from a power amplifier 4| which is excited by a master oscillator 42 in a well known manner..

The power amplifier 4| is modulated by the modulator amplifier 43 in the usual manner. A rectifier 45 supplies plate energy for both the power amplifier 4| and modulator 43. The amount of energy supplied by the rectifier 45 is variable and is controlled in accordance with the setting of an auto-transformer 46.

This transformer is varied by the rotation of the shaft 41 to which is secured a gear 43. This gear meshes with a rack 49 which is slidably mounted in brackets 50. At its upper end the rack 49 is provided with a roller 5| which enages the periphery of the cam 22 and is held against this cam by means of a compresionspring 52 acting against a collar 53 attached to the rack 49.

The master oscillator 42 may be supplied with fixed plate potential from a power pack 55. A monitor 56 may be suitably coupled to the output of the power amplifier for observing and indicating the carrier frequency, carrier strength, and modulation.

Power is supplied to the power pack 55, amplifier modulator 43, rectifier 45, transformer 45, and motor 21 from an A. 0. power line 53.

It is to be understood that the rectifier 45, the amplifier modulator and tone oscillator 43, the power amplifier 4|, the monitor 56, the master oscillator .42, and the power pack are of well known and standard construction containing the usual vacuum tubes and control circuits arranged to excite the radiator II with a modulated carrier in the short wave range toemit a directional radio beam whichiswell known in the art.- Consequently they have not been shown in detail.

The strength of the-carrier is varied by means of the cam 22, acting on the auto-transformer 46 to control the power supplied from the rectifier 45 to the amplifier modulator 43' and the power amplifier 4|. v y

In the operation of the transmitter shown in which is dependent upon the setting of the auto transformer 46, which in turn is dependent upon the shape of the cam 22;.

The energy produced by the power amplifier 4| is tonally modulated by the energy from the amplifier modulator and tone oscillator 43, so

that there is radiated along the radio beam line H a signal having constant audible tone which varies in intensity with the shape of the cam 22. When the key 40 is closed, due to the rotation of the record 33, the tone modulation produced by the amplifier modulator and tone oscillator 43 is changed and therefore the pitch of the signal radiated along the beam line 4 is changed accordingiy.

It is thus seen that each time a group of dots and dashes 31, 33, 39, etc. operates the key 40 a corresponding series of variations in tone will be produced in the radio beam emitted by the radiator The ,shape of the cam 22' is determined as shown in 2, which depicts an island 60, surrounded by a dotted line 6| representing the contour of the bottom of the sea at a given depth, say 30 feet, inside of which it would be dangerous for,shipping to navigate. The cam 22 is constructed with a contour which is a mirror image of the dotted line 6|. The center of the cam 22 is determined by the position of the point 62 on the island 60 where the transmitter shown in Fig. 1 is located.

As the motor 21 drives the shaft I8 at a uniform speed the radio beam will rotate slowly in a counter clockwise direction. At the same time the cam 22 and the signal record disc 33 will rotate in a counter clockwise direction at the same speed. As the dots and dashes 35 and 36 on the disc 33 engage the key 40, signals of modulated energy will be sent out along the beam. These signalswill vary in energy in accordance with the contour of the cam 22, as already described, so

. that the signal strength of the beam, as the beam rotates, will be thesame atall points on the contour line 5 l.

The dashes 36 are positioned with respect to the points of the compass, so that the middle of the dash 36 of the group 31 will be located under the key 4|! when the beam is pointing due north; the middle of the dash 36 of the group 33 will be under the key 40, as shown in Fig. 1, when the beam is pointing northwest; etc. As the beam approaches the points of the compass: north,

northwest, etc., thedots 35 will cause groups of short signals to be sent out along the beam. Thus as the beam approaches north one short signal will be sent out followed by a long signal the middle of which will occur when the beam is due north. As the beam approaches northwest two short signals will be sent out followed by a long signal. In this way each point of the compass will be designated by a designating signal followed by a dash and in each case the signal strength along the contour line 6| of dangerous waters will be constant. It will be understood determined by suitable measuring apparatus, to be described, which can also be used to receive that in place of dots preceding the indicating dash, any suitable combination of dots and dashes may be used for designating the bearing at which the beam will be directed when the indicating dash is sent. Furthermore the direction may be indicated by the beginning or end of the long dash instead of by the middle thereof.

The microphone 34 is used for communication purposes on the beam in case it is desired to check up on the operation of the systemor to send messages to the approaching vessel. In this case, the microphone circuit will replace the keyed oscillator as a source of modulating energy In Fig. 3 is shown a modified form of transmitter in which the disc 33 is replaced by a gear 65, which through a train of gears 66 drives a sprocket wheel 61 at a relatively high speed.

Passing over the sprocket wheel 61 is a continuous I film 08 which also passes over a second sprocket wheel 89. On the film 68 is a spiral sound track with various numbers recorded thereon such as one, two, three, etc. or the words north, northwest, west, etc. Between these words is recorded a uniform audible tone.

Located behind the film 68 is a lamp I0 the light from which passes through the film, an aperture plate II and a lens I2 and is focused upon a photo-electric cell 13. The aperture plate II, lens I2 and cell 13 are mounted on a movable carriage 15 which moves across the top of a casing I6. The carrlagel5 moves so that the light from the lamp I0 always'passes through the spiral record on the film 88. At the end of this record the carriage I5 automatically snaps back to its initial position and starts over again. This mechanism is of well known and standard construction and need not be more fully described herein. The photo-electric cell I3 is connected to the amplifier modulator 43 to replace the microphone 34 as a source of modulating energy.

The shaft I8 may also be extended to the rightand have secured to its end a beveled pinion which meshes with a beveled gear 8I.. Secured to this gear is a parabolic reflector 82 at the focus of which is mounted a lamp 83 which throws a beam of light 85 along the axis of the parabolic reflector 82. v

In the operation of the modified form of transmitter shown in Fig. 3, the mechanism is so arranged that, when the radio beam points north,

the word fnorth of the record on the film 68 will be transmitted by the radio beam. When the beam points northwest, the word northwest will be transmitted, etc. The light beam 85, which may constitute the beam of the lighthouse at which the transmitter is located, will also rotate in synchronism with the radio beam.

The transmitter is therefore characterized by the establishing of a standard field strength at the border line between safe and unsafe waters. For example, the standard frequency might be megacycles, the standard modulation frequency 800 cycles, and the standard field strength 10,000 microvolts per meter at 60 per cent modulation at a point 100 feet above the water along the danger line. This standard field strength occurs at different points along the depth contour line in succession, and the position of the point onthe contour line at which it exists is indicatedby designating signals, at frequencies other than the standard 800 cycles.

Hence, by determining strength and the direction of the beam as it Sweeps past the vessel,- the exact position thereof can be ascertained. The field strength can be the maximum field the signal indicating direction.

In the above embodiment the beam is varied to produce a constant field strength along the contour line. The system could also be used to emit a beam of constant intensity in which case a chart would be employed on the vessel to show the variation in field strength along the contour line, or the chart could show concentric lines of equal field strength with the danger line superimposed thereon. The direction would then be determined in the same manner as above described and the field strength measured. Reference to the chart would then give the exact location of the vessel and distance from the danger line.

In Fig. 4 is shown a receiving and calibrating system for receiving the energy radiated along the beam, and determining the location of the ship carrying the receiver. This system is located upon the approaching vessel and comprises an antenna 90, which is connected by a transmission'cable III to an attenuator 92 which in turn is coupled to a receiver 93. A calibrator 95 is coupled to the antenna system and is connected by a two wire cable 98 and a three wire cable 91 to calibrator control 98 and by a two wire cable-99 to an indicator system I00 which is also connected to the calibrator control 98.

The attenuator system 92 is provided with two double-pole, double-throw switches IM and I02 for throwingin or out the attenuator 92 which is only used during calibration of the receiver. The energy passing through switch I02 is coupled to the receiver 93 by means of a transformer I03. The receiver 93 is shown as of the regenerative type and comprises a detector stage I04, with the usual regeneration and tuning controls, and an audio-frequency amplifier stage I05. Across the output of the receiver 93 are headphones I06. The output circuit of the receiver 93 is also connected through a double-pole, singlethrow switch I01 to the indicator I00. The receiver 93 is shown in simplified form in Fig. 4. It is to be understood that any standard type of receiver may be used and that the above showing is. only for purposes of illustration. The att'enuator 92 may also be of any standard type.

The indicator I00 comprises a meter I08, op-

erative either upon direct or alternating current by use of rectifier system I09 and provided with a pointer IIO.

If a vessel I I I is approaching the island 60 from the northwest as shown in Fig. 2 the energy sent out by the radio beam will be picked up by the antenna 90 and, after bypassing the attenuator 92, will be detected, and the resultant audio signal amplified by the amplifier I05and fed to the indicator I00 where the intensity of the received energy will be indicated on the meter I08, thus indicating the field strength at the antenna 90. As the vessel approaches the island 80 the maximum field strength during each rotation of the beam will increase and the pointer IIO of the meter I 08 will move to the right, indicating the increase in this field strength.

When the approaching vessel reaches the position indicated by the dotted line II5 where it is just entering the danger zone 6|, the field strength of the beam at the maximum of the beam will be of predetermined intensity as described in connection with the transmitter shown cause the pointer IIO to point to a red line IIG marked on the meter I08 or may be read directly from the meter. If the vessel approaches nearer to the island 60 than the line GI as shown at I I2 the field strength at the antenna will increase, thus causing the pointer II 0 to move to the right of the line II6 on the meter I08.

It is thus seen that the navigator of a vessel approaching the island 80 would know, by watching the pointer IIO just when he was crossing the line GI and entering dangerous waters. As long as the pointer IIO remained to the left of the line II 6 the navigator would know that he was in safe waters, but as soon as it crossed the line II6 to the right he would know that he was entering dangerous waters and would steer his vessel accordingly. With a constant beam he would read the field strength and refer to his chart for his position.

As described in connection with Fig. 1 the tone of the radio beam I4, as it rotates, is varied to produce a series of dots followed by a dash. The number of these dots varies with the position of the beam, as for example one dot may be transmitted as the beam approaches north, two dots as it approaches northwest, three dots as it approaches west, etc. In this way the navigator may determine his direction withrespect to the transmitter located at 82 by noting the number of dots sent at the time of greatest intensity of signal. It will be understood that the signals used will be sumciently strong as to be audible even'when the beam is ten to thirty degrees away from the maximum. The dash is so located that its mid-point or other known point, will occur when the beam is pointing due north, due northwest, due west, 'etc. In this way the navigator may be able to determine his position with great accuracy. In case the line 8| is very irregular, the line of equal field strength may be somewhat distorted, so that the point of maximum intensity may not occur directly along the axis of the beam. In case this effect should befound to exist, the dashes 26 on the record disc 22 may be displaced suificiently to correct for this discrepancy.

In practice it would be found that the indication of the meter I08 would be subject to drift due to variations of receiver adjustment, deterioration of tubes, etc., so that it is preferable to provide a calibration circuit so that the receiver may, by adjustment of its controls, correctly indicate the field strength.

For this purpose the calibrator is provided andis preferably located near the antenna system to which it may be coupled by a transformer H1, and is used to produce in the antenna system a signal of the same general characteristics as the incoming signal and of known characteristics as to signal strength and modulation. This calibrator may be used from time to time for the purpose of adjusting the receiver to its proper setting.

The calibrator comprises an oscillator II8 by which energy is generated, preferably of half the frequency radiated by the beam. This oscillator may be of the well known Hartley type which permits the oscillator coil II9 to be tapped at the ground point of the system. The oscillator II8 may be suitably modulated by power, for example at 800 cycles, from an oscillator I20, located in the calibration control system 88, and

i sent up the cable 98, which feeds through a Three sets of rheostats I22, I22 and I24 are provided in the oscillator" for controlling the energy, degree of modulation and filament voltage, respectively.

The output of the. oscillator H8 is fed through two resistors I26 and I21, tapped on the oscillator coil 8, to two plates of a double rectifier I22. This rectifier produces; (1) direct current by'which the strength of signals of the oscillator is indicated, (2) tonal currents by which the modulation of the signals of the oscillator are indicated, and (3) energy of double the frequency of the oscillator, by which the antenna circuit of the receiver is excited. Between the cathodes of the rectifier I28 and ground are connected in series a resistor I28 and a condenser I20, by which direct current and tonal current are sent down the two wire cable 99 to the indicator system I00. A blocking condenser I3I is connected between the cathodes of the tube I28 and the primary of the transformer II1 which energizes the receiving antenna.

By this system it is possible to excite the receiver locally with the same type of signal as transmitted by the beam and at the energy level corresponding to the standard signal produced by the transmitter along the contour line. The energy and degree of modulation may be of a fixed value and may be determined by the reading of the meter I08 and adjusted by rheostats I22 and I22.

The calibration may be eflected by first throwing the switch I22 to the left and closing the switch I 25 to feed the radio frequency energy from the rectifier I28 into the calibrating system where it is indicated on the meter I08. This is adjusted to a standard value by the rheostat I22. The calibrator 85 is now supplying a predetermined standard excitation. The switch I22 is then thrown to the right and the switch I22 is closed to feed the tonal A. C. output of the rectifier I28 to the indicator I00. The meter I08 now shows the modulation which is adjusted to a standard value by the rheostat I22.

When the carrier strength and modulation have been properly set to the standard value as above described, by adjustment of rheostats I22 and I22, the attenuator 82 is connected in the transmission line by closing switches IOI and I82 and the output of the receiver 93 is connected to the indicator I00 by closing the switch I01. The calibrator now energizes the receiver with a signal which produces the same response as the beam signal at the contour line. The receiver is now adjusted, preferablywhen the beam is directed away from the ship, by adjusting the receiver regeneration, and tuning, etc. until the standard output is obtained, as indicated, for example, by the needle IIO registering with the red mark H8. The receiver is now in condition to correctly indicate the field strength of the transmitted beam. It is to be understood that suitable. attenuation networks may be incorporated in the circuits with the various-switches I01, I35 and I28 to produce the desired reading on the meter I08 when the correct adjustments are made. To simplify the manipulation the attenuation may be such that the reading is taken at the red line II6 in each instance.

When theswitch I21 is closed, the signal voltage of oscillator I20 may be read on the meter I08. When the switch I28 is ciosed, the plate voltage of the oscillator II8 "may be read on the meter I08, and when the switch I28 is closed, the filament voltage of thisoscillator may be read on the same meter. These three switches are provided for checking the performance of the calibrator and receiver circuit, and the rheostats I22, I23, and I24 may be marked with red lines indicating when tubes should be replaced to insure that the standard signal can be attained.

Further, any abnormality in setting necessary for-- obtaining the required signal indication may indicate that the antenna system should bechecked up. These switches I31, I38 and I39 and their associated circuits may be omittedif such measurements are not required.

When the modified form of transmitter shown in Fig. 3 is used the constant pitch tone recorded on the film 68 will be heard in the headphones I06 broken by the words north, northwest, west", etc. By listening to the word which is nearest to the point of loudest intensity of the tone the navigator will know his position with respect to the transmitter 62.

It will be understood that the transmitter beam is monitored as to strength and modulation, and that the receiving equipment may be checked from time to time by placing the ship at a calibrating location. the calibration system can be omitted and the receiver can be checked in other ways, as by comparing with a calibrated receiver from time to time or receiving a standard signal the value of which is known.

It is noted that the embodiment of the invention above described provides a system which may be readily and conveniently used for indicating the position of vessels with respect to a given locality. This system can be used in conjunction with the usual lighthouse service or may be supplemental thereto. It is to be understood that only so much of the system has been shown as is necessary to an understanding of the invention and that many of the parts incorporated therein are of standard and well known construction. The invention is, accordingly, not to be limited to the particular form of equipment shown, but various changes and modifications may be made therein as will appear to a person skilled in the art. The invention is only to be limited in accordance with the following claims when interpreted in view of the prior art.

What is claimed is:

l. The method determining position which comprises producing a substantially horizontal beam of radiant energy, rotating said beam about a vertical axis, varying the strength of said beam in synchronism with the rotation thereof so as to circumscribe the source with an irregular line of equal field strength having a predetermined contour, and determinig at a receiving point the maximum field strength of said beam as it sweeps past said point to thereby indicate the position of said point with respect to said contour line.

2. The method of determining position which comprises producing a substantially horizontal beam of radiant energy, rotating said beam about a vertical axis, varying the strength of said beam in synchronism with the rotation thereof so as to circumscribe the source with an irregular line of equal field strength having a predetermined contour, transmitting a signal synchronized with the rotation of said beam to designate the different angular positions thereof, determining at a remote point the maximum field strength of said beam as it sweeps past said point as an indication of distance with respect In certain instances to said contour line and simultaneously receiving the signal to determine the direction of said beam at its point of maximum intensity.

3. The method of determining position which" positions thereof, determining at a remote point the maximum field strength of said beam'as it sweeps past said point as an indication of distance with respect "to said contour line and simultaneously receiving the signal to determine the direction of said beam at its point of maximum intensity.

4. A navigational system comprising means'to produce a horizontal beam of radiant energyhaving a field strength decreasing as the function of the distance from its source, means rotating said beam about a vertical axis and means varying the strength of said beam in synchronism with its rotation so as to circumscribe the source with an irregular line of equal field strength having a predetermined contour and a receiving station having means to determine the maximum field strength of said beam as it sweeps past said point to thereby indicate the position of said point with respect to said contour line.

5. A navigational system comprising means to produce a substantially horizontal beam of radiant energy having a field strength decreasing as a function of the distance from its source, means rotating said beam about a vertical axis, means varying the-strength of said beam in synchronism with the rotation thereof so as to circumscribe the source with an irregular line of equal field strength having a predetermined contour, means transmitting a signal varying in synchronism with the rotation of said beam to designate the different angular positions thereof, and a receiving station comprising means to determine the maximum field strength of said beam as it sweeps past said station as an indicator of distance from said contour line and means to simultaneously receive said signal for determining the direction of said beam at its point of maximum intensity.

6. A navigational system comprising means to produce a substantially horiontal beam of radiant energy having a field strength decreasing as a function of the distance from its source, means rotating said beam about a vertical axis, means varying the strength of said beam in synchronism with the rotation thereof so as to circumscribe the source with an irregular, line of equal field strength having a predetermined contour, means modulating said beam with a signal varying in synchronism with the rotation of said beam to designate the diflerent angular positions thereof, and a receiving, station comprising means to determine the maximum field strength of said beam as it sweeps past said station as an indicator of distance from said contour line and means to simultaneously receive said signal for determining the direction of said beam at its point of maximum intensity.

JOHN HAYS HAMMOND. Jl. 

